This invention pertains to the field of oil refining and the petrochemical industry, and more particularly to installations for the vacuum distillation of liquids, such as crude oil for example. The invention can be used for the rectification of an oil stock.
An installation for distilling a liquid product is known, which has a vacuum rectification column and a steam-driven jet apparatus producing a vacuum in the column (see U.S. Pat. No. 2,680,709, cl. 202-204, 1954).
The main imperfections of this installation are contamination of a base product with water and partial entrainment of the base product with the motive steam conducing, in its turn, to contamination of the steam. These operational features reduce the efficiency of the installation.
A plant for the distillation of a liquid product disclosed in RU patent No. 2048156 has been chosen as the starting point for the invention. The plant has a vacuum rectification column with pipes for feeding a stock product and for bleeding a gas-vapor phase and at least one liquid fraction. Further the plant has a vacuum-producing device composed of a liquid-gas jet apparatus whose gas intake is connected to the pipeline for bleeding a gas-vapor phase, a pump whose discharge side is connected to the liquid inlet of the jet apparatus and a separator connected to the suction side of the pump and furnished with a pipeline for discharge of a compressed gas (see RU patent No. 2048156, cl., B O1 D 3/10, 1995).
In this plant condensation of condensable components of the gas-vapor phase takes place during evacuation of the gas-vapor phase from the rectification column because a motive liquid medium of the vacuum-producing device and the gas-vapor phase are cognate mediums. Environmental pollution is minimal in this case.
An imperfection of the plant is the practical impossibility of ensuring complete condensation of the condensable vapor components prior to entry of a mixture of mediums into the separator, i.e. during mixing of the mediums in the jet apparatus. Although the complete condensation is theoretically possible, it is very hard-to-reach in this plant. Additionally, optimum renewal of the motive liquid medium circulating in the vacuum-producing device is not ensured when the liquid fraction is fed from the rectification column to the separator. The latter reduces efficiency of the liquid-gas jet apparatus.
The present invention is aimed at an increase in efficiency of the plant for the vacuum distillation of a liquid product due to more optimal renewal of a liquid medium circulating in the vacuum-producing device of the plant, more intensive condensation of a gas-vapor phase and providing favorable conditions for completion of the condensation process during mixing of the liquid medium and gas-vapor phase prior to entry of the mixture of mediums into the separator of the plant.
The stated objective of the invention is achieved because the plant for the vacuum distillation of a liquid product, which has a vacuum rectification column with pipelines for feeding a stock product, for bleeding a gas-vapor phase and for bleeding at least one liquid fraction, a vacuum-producing device composed of a liquid-gas jet apparatus whose gas intake is connected to the pipeline for bleeding a gas-vapor phase, a pump whose discharge side is connected to the liquid intake of the jet apparatus, a separator connected to the suction side of the pump and furnished with a pipeline for discharging compressed gas, is furnished further with a jet pump. A nozzle of the jet pump is connected to the pipeline for bleeding the liquid fraction, an inlet of an evacuated medium of the jet pump is connected to an outlet of the liquid-gas jet apparatus and an outlet of the jet pump is connected to the separator. In addition, the plant can be furnished with an additional pump whose suction side is connected to the separator and discharge side is connected to the nozzle of the jet pump.
Experiments have proved that the availability of a jet pump in the contour of the circulation of a motive liquid and feeding a liquid fraction from the rectification column into a nozzle of the jet pump as an active medium improve simultaneously several parameters impacting efficiency of evacuation of a gas-vapor phase:
First, backpressure at the outlet of the liquid-gas jet apparatus is reduced, and consequently the evacuation capability of the apparatus is increased;
Secondly, mixing of the liquid working medium and the gas-vapor phase is intensified;
Thirdly, introduction of the liquid fraction into the contour of the circulation of the liquid working medium prior to entry of the liquid working medium into the separator provides for an entry of a more uniform mixture of mediums into the separator. As a result, the performance of the separator is optimized and the effectiveness of the degassing of the mixture in the separator rises.